Small bird of the Paridae family, order Passeriformes, in North America. There are seven species, all but one exclusive to North America. They are all active, dark-capped, pale-cheeked birds. The commonest species is the black-capped chickadee, Parus atricapillus, which looks very like the willow tit, P. montanus, of Eurasia. It is considered by some authorities to be a subspecies of the latter.